JP2006027298A - Tire air pressure drop alarm device, method, and tire pressure reduction evaluation program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire air pressure drop alarm method, a device, and a tire pressure reduction evaluation program which detect with ease that four wheels are decompressed at the same time even when a vehicle is not in a state of rotation under the travelling condition that the vehicle has driving force. <P>SOLUTION: The tire air pressure drop alarm device is provided with a means of determining whether driving force is exerted on each wheel, a means of computing vehicle speed at the time when the driving force is exerted on each wheel, a means of comparing an average of the rotation speed of a drive wheel relative to an average of the rotation speed of a driven wheel with the average of the rotation speed of the drive wheel relative to the average of the rotation speed of the driven wheel under normal air pressure conditions under the travelling condition that the vehicle has a driving force, and a means of evaluating that the air pressure of all the wheels attached to the vehicle is reduced at the same time, or that the air pressure of the drive wheel is reduced as a result of the comparison. Moreover, the average of the rotation speed of the drive wheel relative to the average of the rotation speed of the driven wheel under normal air pressure conditions is changed in accordance with acceleration and deceleration of the vehicle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for detecting a decrease in air pressure of each tire of a vehicle. More specifically, the present invention relates to a tire pressure drop warning device that more reliably performs tire pressure drop determination when all wheels are depressurized simultaneously.

  The tire pressure gradually decreases even if the tire is not damaged. In addition to simultaneous decompression due to dimensional growth of a new tire and a decrease in temperature, simultaneous decompression may occur because air permeates the tire rubber. In such a case, the four wheels often depressurize at the same time, and it may not be noticed that the depressurization is occurring. Driving with reduced pressure is sometimes dangerous, and also worsens fuel consumption, so there are concerns about the impact on the environment.

  Therefore, conventionally, a method for detecting that four wheels are simultaneously depressurized has been proposed in addition to detecting the depressurization of one wheel.

  For example, the inclination of the relationship between the pressure reduction judgment value (DEL value) and the lateral acceleration (lateral G) based on the difference between the sum of the two rotational speeds of the wheels located on the diagonal of the vehicle, the yaw rate sensor value, and the rotation of the left and right wheels From the relationship of speed ratio, there is a method of detecting simultaneous reduction of four wheels using a difference in load sensitivity.

  In addition, for example, there is a method of detecting simultaneous pressure reduction of two drive wheels by utilizing a change in friction factor-slip rate (μ-s) characteristics (Patent Documents 1, 3, 4, and 5). The method using the change in the μ-s characteristic can also detect simultaneous four-wheel pressure reduction. In addition, it is possible to detect the pressure reduction of the two coaxial wheels by comparing the rotational speed ratio of the front and rear wheels with the rotational speed ratio of the front and rear wheels at normal air pressure when the vehicle has no driving force. Reference 2) and a method for detecting four-wheel simultaneous decompression are available.

JP 2004-17717 A Japanese Patent Laid-Open No. 2003-220811 JP 2003-291616 A JP 2003-326927 A Japanese Patent Laid-Open No. 2003-267012

  However, in the conventional method using load sensitivity, since it cannot be determined unless the vehicle is turning, it is possible to detect simultaneous four-wheel depressurization until the vehicle continuously turns for the time required for the determination. Can not. In the method using the change in the μ-s characteristic, the change in the μ-s characteristic is small, and it is necessary to calculate the slope of the μ-s characteristic curve by regression calculation. Therefore, a certain time is required for data analysis. . Moreover, in the method using the rotational speed ratio between the front and rear wheels, the pressure reduction can be detected only when the vehicle does not have a driving force.

  Therefore, the present invention provides a tire pressure drop alarm method and apparatus, and a tire decompression determination program for easily detecting that the four wheels are decompressed at the same time even when the vehicle has a driving force and is not in a turning state. The purpose is to provide.

  Originally, the method of comparing the rotation speed ratio of the front and rear wheels before and after the pressure reduction can detect the pressure reduction of the two coaxial wheels, but the pressure reduction is the same for both the front and rear wheels in the four wheel pressure reduction. There was no change, and it was thought that simultaneous reduction of four wheels could not be detected by comparing the rotation speed ratio. In addition, the driving braking force is regarded as an error factor when calculating the rotation speed ratio of the front and rear wheels, and the conventional method uses only data on the running state (idle running state) in which the vehicle has no driving force. It was.

  However, applying the characteristic that the load sensitivity decreases when the wheel is depressurized, except for certain conditions, the front and rear wheels of normal air pressure in a traveling state where the vehicle does not have driving force even when the four wheels are depressurized simultaneously. It was found that the rotation speed ratio of the front and rear wheels when the pressure is reduced changes compared to the rotation speed ratio of. If this is further extended, in a traveling state having a constant driving force that is not zero, it is possible to capture the change in the rotational speed ratio of the front and rear wheels when the pressure is reduced compared to the rotational speed ratio of the front and rear wheels of normal air pressure. Yes, it is possible to determine simultaneous depressurization of four wheels.

  In this case, it is known that when the pressure is reduced, the μ-s characteristic of the tire changes and the slip becomes smaller. Therefore, due to a synergistic effect with a decrease in load sensitivity due to the pressure reduction, the rotational speed of the front and rear wheels at the time of simultaneous reduction of the four wheels is reduced. The change in ratio is greater.

  In general, as the vehicle speed increases, the driving force for maintaining the speed also increases. Therefore, by collecting data on the rotational speed ratio of the front and rear wheels at a constant speed at a certain high speed, it is possible to collect data on a running state having a constant driving force that is not zero (during normal time and reduced pressure). Further, the rotational speed ratios of the front and rear wheels in a range where the acceleration is constant may be collected and compared.

  The tire pressure drop warning device of the present invention is a tire pressure drop warning device having means for detecting the rotational speed of a wheel mounted on a vehicle and means for judging a tire pressure drop from the rotational speed information of the wheel. Means for determining whether a driving force is applied to each wheel, a means for calculating a vehicle speed when the driving force is applied to each wheel, and a driven wheel in a traveling state where the vehicle has a driving force. Means for comparing the average rotational speed of the driving wheel with respect to the average rotational speed of the driven wheel to the average rotational speed of the driven wheel with respect to the average rotational speed of the driven wheel at normal air pressure, and the result of the comparison is attached to the vehicle. Means for determining that all the wheels are simultaneously depressurized or that the drive wheels are depressurized.

  The tire pressure drop alarm device according to the present invention is characterized in that the average rotational speed of the drive wheels with respect to the average rotational speed of the driven wheels at the normal air pressure changes according to the acceleration / deceleration of the vehicle.

  According to the present invention, it is possible to detect that all the wheels are depressurized at the same time or the simultaneous depressurization of the drive wheels based on the rotational speed information of the wheels. Moreover, it can be determined in the drive state, and is not limited to turning. In vehicle travel (except for the stop time), the time in the driving state with driving force is longer than the time in the idling state, so that the time until pressure reduction is detected can be shortened and the accuracy of detection Will improve.

  Further, unlike the case where only the μ-s characteristic change is used, it is not necessary to obtain the slope of the μ-s characteristic curve by calculating the regression line, and the pressure reduction can be determined easily and accurately.

Embodiment A tire pressure drop alarm device according to the present invention will be described with reference to FIG.

  The tire pressure drop alarm device 10 in the present embodiment is connected to the means 2 for detecting the rotational speed of each wheel, and is connected to the tire air pressure alarm display device 7. Further, the tire pressure drop alarm device is connected to means 1 for detecting whether or not driving force is acting on the wheel, for example, a detector for torque applied to the drive shaft or a detector for accelerator operation. The tire pressure warning device 10 is configured to issue a warning to the calculation device 4, a memory 5 for storing a program and calculation data, an input device for inputting data from the driving force detection device 1 and the wheel rotation speed detection device 2, and a tire pressure warning display device 7. An output device 6 for outputting is provided. In addition to the rotational speed of the wheels, the speed of the vehicle may also be detected and input. Further, the tire pressure drop alarm may be output to another vehicle control device 8 or the like. In addition, a device for inputting a reset switch for initializing data and a signal indicating that the engine has been started is connected (not shown).

  In the present embodiment, it is described that the tire pressure drop determination program and data are stored in the same memory, but the tire pressure drop determination program is stored in ROM (read only memory) and the data is stored in RAM (random access). (Memory). The rotational speed ratio of the front and rear wheels at normal air pressure is stored in the RAM, but the storage portion is backed up by a nonvolatile memory or a battery.

  Hereinafter, based on FIGS. 2 to 4, the principle of the four-wheel simultaneous decompression detection of the present invention will be described.

  FIG. 2 is a diagram showing a change in dynamic load radius due to a load in a front-wheel drive vehicle in comparison with normal air pressure and four-wheel depressurization. The radius of the tire changes with the load. In a front-wheel drive vehicle, the front wheel usually has a larger load, and the drive wheel slips during traveling, so that the rotational angular velocity is higher than that of the driven wheel, and the tire radius is apparently reduced. However, when the tire air pressure decreases from normal, the difference in decrease due to the load of the driving wheel and the driven wheel becomes small (in the case of right side of FIG. 2, four-wheel depressurization). Therefore, the ratio of the dynamic load radii of the front and rear wheels when the four wheels are depressurized from the ratio of the dynamic load radii of the front and rear wheels when the air pressure is normal (the dynamic load radius of the drive wheels to the dynamic load radius of the driven wheels) ( The dynamic load radius of the driving wheel relative to the dynamic load radius of the driven wheel is large. When the vehicle is traveling straight, the tire peripheral speed is the same for all four wheels. Conversely, when the air pressure is normal, the ratio of the rotational speeds of the front and rear wheels (rotational angular speed x tire radius) to the rotational speed of the driven wheels The ratio of the rotational speeds of the front and rear wheels when the four wheels are depressurized is smaller than the rotational speed of the drive wheels.

  FIG. 3 is a graph showing the relationship between four-wheel pressure reduction and front-rear wheel rotational speed ratio (average rotational speed of driving wheels relative to average rotational speed of driven wheels; hereinafter abbreviated front-rear wheel speed ratio) in several vehicle types. It is. Here, the average rotational speed of the driven wheels (or driving wheels) means that when the number of driven wheels (or driving wheels) is two, the sum of the rotational speeds of the two driven wheels (or driving wheels) is divided by two. When the number of driven wheels (or drive wheels) is one, it means the rotational speed of that one wheel. The front-rear wheel speed ratio is reduced as the tire air pressure decreases in FF vehicles (engine front, front wheel drive) sedan, FR vehicles (engine front, rear wheel drive) sedan, and FF vehicle SUV (Sport Utility Vehicle). Is decreasing.

  Therefore, when the front / rear wheel speed ratio is smaller than the front / rear wheel speed ratio at normal air pressure by a certain value or more, it can be determined that the four wheels are depressurized. Even when the two driven wheels are depressurized, the front-rear wheel speed ratio is small, so it is impossible to distinguish between four wheel depressurization and two driven wheel depressurizations. Since the front-rear wheel speed ratio is larger (close to normal), the pressure reduction judgment is made with the threshold value when the four wheels are depressurized taking the safety side.

  When the two driving wheels are depressurized, the dynamic load radius of the driven wheel does not change, and the dynamic load radius of the driving wheel is smaller than that at normal air pressure, so the front-rear wheel speed ratio is larger than that at normal air pressure. . Therefore, when the front-rear wheel speed ratio is larger than the normal air pressure by a certain value or more, it can be determined that the two drive wheels are depressurized.

  When either the driving wheel or the driven wheel is one wheel, that is, the vehicle has three wheels, the average rotational speed of the driving wheel or the driven wheel is the rotational speed of the one wheel itself. In the above description, the case where the vehicle has four wheels has been described. However, even when the vehicle has three wheels, the same principle can be applied to detect the three-wheel pressure reduction or the pressure reduction of the driving wheel (two wheels or one wheel). In the following description and examples, a four-wheel vehicle will be described, but the same applies to a three-wheel vehicle.

  FIG. 4 is a graph showing an example of the relationship between the acceleration / deceleration of the vehicle and the front / rear wheel speed ratio in the case of an FF vehicle sedan. As described above, the front-rear wheel speed ratio is smaller when the four wheels are depressurized than when the tire pressure is normal (the lower line in FIG. 4). As the speed (G) increases, the front / rear wheel speed ratio increases. This is because when the driving force is applied, the dynamic load radius of the driving wheel becomes small due to slip or the like. Further, the increase in the front / rear wheel speed ratio due to the increase in acceleration is greater when the tire pressure is normal.

  Therefore, the front and rear wheels measured by changing the front / rear wheel speed ratio of the normal air pressure according to the acceleration / deceleration when measuring the front / rear wheel speed ratio during traveling to determine whether the four wheels are depressurized or two drive wheels are depressurized. If compared with the speed ratio, it can be determined more accurately.

  Next, the operation in the embodiment of the present invention will be described with reference to FIG.

  In a step different from the flowchart shown in FIG. 6, a mode for collecting initial data may be set, for example, when a tire is changed or a tire is rotated.

  In step S1, a data input command is issued to the input device, and wheel rotational speed information is taken into the memory. The rotational speed information is calculated by multiplying the rotational angular speed of the wheel by the tire radius. The rotational angular velocity of the wheel may count pulses detected as the wheel rotates, or may measure the pulse interval. Moreover, you may use the measuring device from which an output voltage changes according to the rotational angular velocity of a wheel. Accumulate the distance from the start.

  In step S2, it is confirmed whether or not a certain distance has been traveled since the start. No determination is made while the distance is less than a certain distance.

  In step S3, a branch is made as to whether or not to make the following determination based on whether the vehicle speed is equal to or higher than a certain level and whether the driving force is positive. If the vehicle speed is constant and stable and the driving force is positive, the front-rear wheel speed ratio and the vehicle acceleration in step S4 are calculated.

  If the mode is not a mode for collecting initial data (which can be estimated as normal air pressure) (step S5), the front and rear wheel speed ratio is compared with the initial (normal) front and rear wheel speed ratio data (step S6). If the ratio (R / initial value) of the front / rear wheel speed ratio (R) to the normal air pressure front / rear wheel speed ratio (initial value) is greater than a predetermined drive wheel pressure reduction threshold, the drive wheel is depressurized. Therefore, a driving wheel pressure reduction alarm is issued (step S7).

  When it is determined that the R / initial value is not depressurizing the driving wheel (step S8), a four-wheel depressurization alarm is issued when the R / initial value is smaller than a predetermined four-wheel depressurization determination threshold ( Step S9). If neither the driving wheel nor the four wheels are depressurized, the process returns to step S1 to repeat the wheel rotation speed input to determination.

  In the case of the initial data collection mode, the process branches from step S5 to step S10, and the change of the front and rear wheel speed ratio with the previous value is examined. Add (step S11). For example, the data collection averages the front and rear wheel speed ratios for each vehicle acceleration.

  If the predetermined travel distance has elapsed since the reset set in the initial data collection mode (step S12), or if the change in the front and rear wheel speed ratio is greater than or equal to a certain value (step S10), the initial data collection mode is canceled.

  The effects of the present invention will be described below based on specific examples.

EXAMPLE Vehicles used in this example are three types of vehicles: Audi A4 (manufactured by Audi Co., Ltd.), Cedric (manufactured by Nissan Motor Co., Ltd.), and Odyssey (manufactured by Honda Motor Co., Ltd.).

  Table 1 shows the axial loads for the three models. FIG. 5 shows the front-rear wheel speed ratio when the tire pressures of the four wheels are normal, reduced by 20%, and reduced by 40% in the light product and the fixed product of the three vehicle types shown in Table 1.

  With the exception of the Odyssey fixed volume state, the front-rear wheel speed ratio decreases as the four wheels depressurize. In each vehicle type, for example, a four-wheel pressure reduction determination can be performed using a front-rear wheel speed ratio value of 40% reduction in light product as a determination threshold value.

It is a block diagram which shows the structure of the apparatus in embodiment of this invention. It is a figure which shows the change of the dynamic load radius by a load by comparing with normal air pressure and the time of 4 wheel pressure reduction. It is a graph showing the example of the relationship between 4 wheel pressure reduction and the rotational speed ratio of a front-and-rear wheel in this invention. It is a graph showing the example of the relationship between the acceleration / deceleration of a vehicle and the rotational speed ratio of a front-and-rear wheel. It is a graph showing four-wheel pressure reduction detection by the rotation speed ratio of four-wheel pressure reduction and the front-and-rear wheel in the Example of this invention. It is a flowchart in tire decompression determination in an embodiment of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Driving force detection apparatus 2 Wheel rotational speed detection apparatus 3 Input apparatus 4 Arithmetic apparatus 5 Storage apparatus 6 Output apparatus 7 Tire pressure alarm display apparatus 10 Tire pressure alarm apparatus

Claims (6)

A tire pressure drop alarm device comprising: means for detecting a rotation speed of a wheel mounted on a vehicle; and means for determining a tire pressure drop from the rotation speed information of the wheel,
Means for determining whether driving force is acting on each wheel;
Means for calculating vehicle speed when driving force is applied to each wheel;
Means for comparing the average rotational speed of the driving wheel with respect to the average rotational speed of the driven wheel to the average rotational speed of the driven wheel with respect to the average rotational speed of the driven wheel at normal air pressure when the vehicle has a driving force. When,
A tire pressure drop alarm device comprising: means for determining that all the wheels mounted on the vehicle are depressurized at the same time or that the drive wheels are depressurized according to the result of the comparison. 2. The tire pressure drop alarm device according to claim 1, wherein the average rotational speed of the driving wheel with respect to the average rotational speed of the driven wheel at the normal air pressure changes according to the acceleration / deceleration of the vehicle. A tire pressure drop determination method for determining a tire pressure drop using rotational speed information of wheels mounted on a vehicle,
Determining whether a driving force is acting on each wheel;
Calculating the vehicle speed when the driving force is applied to each wheel;
A step of comparing the average of the rotational speed of the driving wheel with respect to the average of the rotational speed of the driven wheel with the average of the rotational speed of the driven wheel with respect to the average of the rotational speed of the driven wheel at normal air pressure when the vehicle has driving force When,
And a step of determining that all the wheels mounted on the vehicle are depressurized at the same time or that the drive wheels are depressurized according to the result of the comparison. The tire pressure drop determination method according to claim 3, wherein an average of the rotational speed of the driving wheel with respect to an average of the rotational speed of the driven wheel at the normal air pressure changes according to the acceleration / deceleration of the vehicle. Computer to determine tire pressure drop,
Memory means for storing the rotational speed of wheels mounted on the vehicle;
Means for determining whether driving force is acting on each wheel;
Means for calculating vehicle speed when driving force is applied to each wheel;
Compare the average rotational speed of the driving wheel relative to the average rotational speed of the driven wheel to the average rotational speed of the driven wheel relative to the average rotational speed of the driven wheel at normal air pressure when the vehicle has a driving force. Thus, a tire pressure drop determination program for causing all wheels mounted on the vehicle to function as means for detecting that the pressure is reduced or that the drive wheel is reduced. The tire pressure drop determination program according to claim 5, wherein the average rotational speed of the driving wheels with respect to the average rotational speed of the driven wheels at the normal air pressure changes according to the acceleration / deceleration of the vehicle.

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